The friction stir welding (FSW: Friction Stir Welding) has been known as a method for joining together metallic components. The friction stir welding is designed to rotate and move a rotary tool along a butting portion of metallic components, force the metal at the butting portion to make in plastic flow resulted from the friction heat between the rotary tool and the metallic component, and join together in solid phase between the metallic components.
In recent years, as electronic devices, for example, personal computers have been developed in performance, calorific value of CPU (heat generating body) boarded therein has been increasing in amount. Then, it has been becoming important to cool down the CPU. Conventionally, although a heat sink typed of air cooling fan has been used to cool down the CPU, problems such as noises caused by fan and cooling limits by air cooling have been gathering attention. Thus, the liquid-cooled jacket has been gathering attention as a next-generation cooling system.
In such a liquid-cooled jacket, an art for joining together between constituent components by the friction stir welding has been disclosed in Japanese Patent Unexamined Laid-open publication No. 324,647 of 2006. The liquid-cooled jacket is, for example, provided with a jacket body having a fin housing for metallic fins and a seal body for the fin housing. Then, it is configured to manufacture the liquid-cooled jacket by the friction stir welding by going round the rotary tool along a butting portion between a peripheral wall of the jacket body surrounding the fin housing and a circumferential surface of the seal body. The seal body is formed to be thinner compared with the jacket body and put on a supporting surface comprising of a bottom surface of a step portion formed in the jacket body. The rotary tool is moved along the butting portion in order to place its center on the butting portion. Then, the jacket body and the seal body are mutually joined together.
As above mentioned, in case where the thin-walled seal body is put on a supporting surface of the jacket body to join together the butting portion by the friction stir welding, it has a problem that the seal body is curved and warped by thermal contraction and expansion owing to the friction stir occurred on a surface of the jacket body.
In order to solve the above problems, an art for emitting a water jet by a cooling nozzle at a place of the friction stir welding and pressing the butting portion by a roller after the friction stir welding has been disclosed in Japanese Patent Unexamined Laid-open Publication No. 87,871 of 2001.